• Elastomers and Composites
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• 제34권3호
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• pp.239-246
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• 1999

폐타이어에서 보강실과 고무로 배합된 부분(side wall)을 아임계와 초임계 상태의 세가지 용매, 물, 28% 암모니아수, 암모니아를 사용하여 용매의 분해와 추출능을 비교하였다. 6mm 입방체로 만든 폐타이어의 초임계물에 의한 분해와 추출속도는 140 kJ/mol의 활성화에너지를 갖는 1차 속도식을 잘 만족하였다. 초임계상태에서 28% 암모니아용액은 압력이 감소할수록 초기추출에서 초임계물보다 추출능이 높게 나타났다. 이 현상은 초임계물에 용해되어 있는 암모니아의 영향 때문이라고 추측된다.

• 한국환경과학회지
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• 제14권10호
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• pp.919-928
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• 2005

This study introduces the development of new supercritical water oxidation(SCW)(multiple step oxidation) to destruct recalcitrant organic substances totally and safely by using sodium nitrate as an oxidant. This method has solved the problems of conventional SCW, such as precipitation of salt due to lowered permittivity, pressure increase following rapid rise of reaction temperature, and corrosion of reactor due to the generation of strong acid. Destruction condition and rate in the supercritical water were examined using Polyvinyl Chloride(PVC) and ion exchange resins as organic substances. The experiment was carried out at $450^{\circ}C$ for 30min, which is relatively lower than the temperature for supercritical water oxidation $(600-650^{\circ}C)$. The decomposition rates of various incombustible organic substances were very high [PVC$(87.5\%)$, Anion exchange resin$(98.6\%)$, Cationexchange resin$(98.0\%)$]. It was observed that hetero atoms existed in organic compounds and chlorine was neutralized by sodium (salt formation). However, relatively large amount of sodium nitrate (4 equivalent) was required to raise the decomposition ratio. For complete oxidation of PCB was intended, the amount of oxidizer was an important parameter.

• Nuclear Engineering and Technology
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• 제40권2호
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• pp.147-154
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• 2008

The general corrosion behavior of austenitic and ferritic steels(316L, 304, N controlled 304L, and 410) in supercritical water is investigated in this paper. After exposure to deaerated supercritical water at $480^{\circ}C$/25 MPa for up to 500 h, the four steels studied were characterized using gravimetry, scanning electron microscopy/energy dispersive X-ray spectroscopy(SEM/EDS), X-ray photoelectron spectroscopy(XPS), and X-ray diffraction(XRD). The results show that the 316L steel with a higher Cr and Ni content has the best corrosion-resistance performance among the steels tested. In addition to the oxide layer mixed with $Fe_{3}O_{4}$ and $(Fe,Cr)_{3}O_{4}$ that formed on all the samples, a $Fe_{3}O_{4}$ loose outer layer was observed on the 410 steel. The corrosion mechanism of stainless steels in supercritical water is discussed based on the above results.

• Nuclear Engineering and Technology
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• 제40권2호
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• pp.127-132
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• 2008

An experimental loop operating with water at supercritical conditions(25MPa, $600^{\circ}C$ in the test section) is designed for operation in the research reactor LVR-15 in UJV Rez, Czech Republic. The loop should serve as an experimental facility for corrosion tests of materials for in-core as well as out-of-core structures, for testing and optimization of suitable water chemistry for a future HPLWR and for studies of radiolysis of water at supercritical conditions, which remains the domain where very few experimental data are available. At present, final necessary calculations(thermalhydraulic, neutronic, strength) are being performed on the irradiation channel, which is the most challenging part of the loop. The concept of the primary and auxiliary circuits has been completed. The design of the loop shall be finished in the course of the year 2007 to start the construction, out-of-pile testing to verify proper functioning of all systems and as such to be ready for in-pile tests by the end of the HPLWR Phase 2 European project by the end of 2009.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2471-2476
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• 2008

Turbulent flow and heat transfer to water at supercritical pressure flowing in vertical pipes is investigated using direct numerical simulation (DNS). A conservative space-time discretization scheme for variable-density flows at low Mach numbers is adopted in the present study to treat steep variations of fluid properties at supercritical pressure just above the thermodynamic critical point. The fluid properties at these conditions are obtained using PROPATH and used in the form of tables in the simulations. The buoyancy influence induced by strong variation of density across the pseudo-critical temperature proved to play an important role in turbulent flow and heat transfer at supercritical state. Depending on the degree of buoyancy influence, turbulent heat transfer may be enhanced or significantly deteriorated, resulting in local hot spots along the heated surface.

• 대한화학회지
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• 제37권6호
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• pp.604-611
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• 1993

초임계 유체 크로마토그래피(Supercritical Fluid Chromatography, SFC)는 종래의 크로마토그래피 방법으로 분석하기 어려운 물질을 분석해 내는 기술로써 발전이 되어왔다. 그러나, SFC에서 이동상으로 많이 사용되고 있는 초임계 C$O_2$는 용매로써 특성이 n-hexane과 매우 비슷하여 극성이 큰 시료들을 용출(elution)시키기가 어렵다. 이러한 점을 해결하기 위하여 초임계 C$O_2$에 극성을 지닌 물질 즉, 변형제(modifier)를 섞어서 이동상으로 사용할 수 있다. 본 연구에서는 초임계 C$O_2$에 변형제를 첨가시키는 새로운 방법을 개발하였고, 변형제로써 초임계 C$O_2$에 첨가된 수분(H$_2O$)의 양을 perfluorosulfonate ionomer(PFSI) film을 이용해 만든 amperometric microsensor로써 측정하였다. 이와같은 방법을 사용함으로써 포화 column보다 상당히 긴 시간동안 일정하게 수분을 첨가할 수 있었고, 실제로 이 방법을 사용하여 순수한 C$O_2$ 이동상만으로는 분리하기 어려운 몇 가지 살균제와 살충제에 적용한결과 좋은 크로마토그램을 얻었다.

• Korean Chemical Engineering Research
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• 제47권3호
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• pp.281-286
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• 2009

아임계 및 초임계 조건의 물을 이용하여 캐나다산 Athabasca 오일샌드로부터 역청 추출 및 황 제거 실험을 수행하였다. 0~120 min의 반응시간, 360, $380^{\circ}C$의 온도, 15~30 MPa의 압력 및 $0.074{\sim}0.61g/cm^3$의 물 밀도를 변화시키면서 micro reactor에서 역청 수율을 조사하였다. 역청 수율은 온도에 상관없이 압력이 증가할수록 증가하였으며, 특히 초임계 영역에서 수증기 개질반응에 의해 생성된 수소에 의해 역청의 수율이 급격히 증가하였다. 전체 기상 생성량은 압력 증가에 따라 감소하였으나 $380^{\circ}C$에서 황과 수소의 생성분율은 25 및 30 MPa로 압력 증가에 따라 소량 증가하였다. 이상의 결과는 초임계 조건이 수소의 생성과 황의 제거에 유리하다는 것을 보여준다. 초임계 조건$380^{\circ}C$, 25와 30 MPa)에서 역청 수율은 최대 약 22%였으며, 오일샌드에 함유된 황 제거율도 최대값 40%에 도달하였다.

• Nuclear Engineering and Technology
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• 제39권4호
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• pp.273-286
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• 2007

This paper presents the research activities performed to date for the development of a supercritical pressure water-cooled reactor (SCWR) in Korea. The research areas include a conceptual design of an SCWR with an internal flow recirculation, a reactor core conceptual design, a heat transfer test with supercritical $CO_2$, an adaptation of an existing safety analysis code to the supercritical pressure condition, and an evaluation of candidate materials through a corrosion study. Methods to reduce the cladding temperature are introduced from two different perspectives, namely, thermal-hydraulics and core neutronics. Briefly described are the results of an experiment on the heat transfer at a supercritical pressure, an experiment that is essential for the analysis of the subchannels of fuel assemblies and the analysis of a system safety. An existing system code has been adapted to SCWR conditions, and the process of a first-hand validation is presented. Finally, the corrosion test results of the candidate materials for an SCWR are introduced.

• 분석과학
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• 제10권2호
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• pp.131-138
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• 1997

초임계 유체 크로마토그래피(Supercritical Fluid Chromatography, SFC)는 종래의 크로마토그래피 방법으로 분석하기 어려운 물질을 분석해 내는 기술로서 발전이 되어 왔다. 그러나 SFC에서 이동상으로 많이 사용되고 있는 초임계 유치 $CO_2$는 용매로서 특성이 n-hexane과 매우 비슷하여 극성이 큰 시료들을 용출(elution)시키기가 어렵다. 이러한 점을 해결하기 위하여 초임계 $CO_2$에 극성을 지닌 물질, 즉 변형제(modifier)를 섞어서 이동상으로 사용할 수 있다. 본 연구에서는 초임계 $CO_2$에 첨가된 수분($H_2O$)의 양을 perfluorosulfonate ionomer(PFSI) film을 이용하여 만든 amperometric microsensor로서 측정하였다. 이와 같은 방법을 사용함으로써 포화 column보다 상당히 긴 시간 동안 일정하게 수분을 첨가할 수 있었고, 실제로 이 방법을 사용하여 순수한 $CO_2$ 이동상만으로는 분리하기 어려운 비타민류의 분석에 적용한 결과 좋은 크로마토그램을 얻었다.

• Bulletin of the Korean Chemical Society
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• 제34권10호
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• pp.2925-2930
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• 2013

We present results of molecular dynamics simulations for hydroxide ion in supercritical water of densities 0.22, 0.31, 0.40, 0.48, 0.61, and 0.74 g/cc using the SPC/E water potential with Ewald summation. The limiting molar conductance of $OH^-$ ion at 673 K monotonically increases with decreasing water density. It is also found that the hydration number of water molecules in the first hydration shells around the $OH^-$ ion decreases and the potential energy per hydrated water molecule also decreases in the whole water density region with decreasing water density. Unlike the case in our previous works on LiCl, NaCl, NaBr, and CsBr [Lee at al., Chem. Phys. Lett. 1998, 293, 289-294 and J. Chem. Phys. 2000, 112, 864-869], the number of hydrated water molecules around ions and the potential energy per hydrated water molecule give the same effect to cause a monotonically increasing of the diffusion coefficient with decreasing water density in the whole water density region. The decreasing residence times are consistent with the decreasing potential energy per hydrated water molecule.